You can use any search engine to find copies of those RFCs.
>I mean : client A is doing a HTTP connection on server B. Is there any
>tool existing that could be on a Client B to monitor what is doing the
>client A ?
>If possible, a graphical tool which would show on the C screen what's
>happening on the browser of A ?

Read the commands and data. It's in text, not pictures.
>I don't want to use VNC, because my point is to debug what's going on
>between A and B, and why some "dialog" fails...

Read the commands and see what is being requested, what is the response,
and what the web page is trying to display. If you don't understand
this, you are going to have a very hard time debugging the connection.